Flight Crew
The flight instructor (CFI) in the right seat was providing dual instruction to the CFI in the left seat, who had no experience in the aircraft type.
Accident Sequence
During the initial climb, at an altitude of approximately 400 to 500 feet above ground level, witnesses heard the engine lose power or surge. The airplane was observed to roll to one side and descend steeply to impact.
Aircraft Modifications
The airplane had been extensively modified with an unapproved wing tip fuel tank system addition. Additionally, a powerplant modification for increased horsepower and other airframe modifications were present, not all of which were documented or approved. The standard factory fuel selector was in the AUX position, and the tip tanks fuel selector valve was in a half-on/half-off position. The fuel selector valve for the tip tanks did not have any placards showing position or operation.
Pre-Flight Instructions
Both CFIs had been given incorrect instructions on how to position the fuel system selector valves by the owner and a mechanic who signed off the annual inspection. This was the first flight since that annual inspection.